1. Field
The present invention relates to a control mechanism for an automotive transmission. More specifically the invention encompasses a fluid control mechanism utilizing at least two control valves and a fluid motor in a fluid circuit to control the actuation of a fluid operable starting clutch and a gear engaging means.
2. Prior Art
The use of control valves to provide fluid flow for gear selection in an automotive transmission and for clutch actuation is known in the art and is shown in several configurations. These configurations include: (1) a slide valve responsive to changes in the acceleration pedal and controlling a forward clutch (U.S. Pat. No. 4,331,045); (2) a drive controlling mechanism with a shuttle valve for control of fluid to and from a parking brake for braking and releasing a rotary shaft of a hydraulic motor (U.S. Pat. No. 4,330,051); (3) a multi valve control mechanism including primary and secondary regulator valves, throttle modulator valve, manual control valve, a downshift valve, throttle valve, servo orifice control valve, two shaft valves and a drive control valve, as well as multiple brakes and clutches as taught in U.S. Pat. No. 3,118,320; (4) a fluid control mechanism for an infinitely variable transmission wherein one control is utilized to control pressure to one variable sheave and a second control valve is utilized to control fluid flow to a second variable sheave, as taught in U.S. Pat. No. 4,152,947. U.S. Pat. No. 4,098,148 discloses the utilization of a planetary over-drive gear mechanism for an automatic transmission, which control mechanism includes two servomotors for a controller and a brake mechanism and an interlock and further incorporates by reference U.S. Pat. No. 3,744,348 which defines a mutliple valve, multiple discrete-ratio gear automatic transmission which monitors a pressure signal that is a function of torque and vehicle speed, and the control circuit includes sequencing valves and servomotors. U.S. Pat. No. 3,115,049, teaches a multiple valve arrangement that is throttle responsive to condition the transmission to allow the engine to operate at a constant speed. U.S. Pat. No. 3,146,630 to Ivey, shows fluid actuated servomotors to change gear ratios in a multiple speed transmission which includes a torque converter and fluid retarder and is impliedly useful in trucks or tractors. U.S. Pat. No. 3,369,430, teaches a transmission control system utilizing a pressure regulating system for pressure control to the friction elements and showing a regulating valve effective at high speed drive ratio to delay the engagement of a servomotor to provide a smooth down-shift, the transmission having multiple gearing, a fluid torque converter and multiple clutches and brakes. U.S. Pat. No. 3,263,782 to Smirl et al., describes a clutch control mechanism responsive to engine speed and torque, and automatic disengagement and re-engagement of the clutch in response to a transmission shift means. U.S. Pat. No. 3,043,152, discloses a CVT control means for adjusting the gear ratio in response to a load on the driver gear (pulley), but does not suggest a change gear relation using a synchronizer and dual servomotor-slide valve control. U.S. Pat. No. 4,253,347, teaches a control system for controlling the gain constant in an orifice valve controlled by oil pressure from a governor valve dependent on rotational speed of an output shaft. U.S. Pat. No. 4,194,608, discloses a control for a countershaft transmission by providing electric control of a hydraulic transmission having multiple clutches and brakes, where the clutch assembly is operable between a coupled and an uncoupled condition by a clutch control valve which is also controlled by electric control means, and U.S. Pat. No. 4,331,046, teaches an automatic transmission control system including multiple discrete gear ratios, multiple clutches and brakes controlled by multiple valves and a valve network responsive to a manually operable valve.